1. Field of the Invention
This invention relates to anti-bacterial compounds and methods of using them to treat bacterial infections.
2. Description of the Related Art
Bacterial resistance to drugs drives a continuing need for new anti-bacterial agents that to which the bacteria have not yet developed resistance. DNA gyrase is an enzyme found in many gram-positive and gram-negative bacteria. It is believed that DNA gyrase participates in the unfolding of the DNA double helix that takes before DNA replication by catalyzing ATP-dependent negative super-coiling of the DNA. DNA gyrase is believed to contain a complex of dimeric subunits, called gyrases A and B, that form an A2B2 active enzyme complex. It is further believed that the A2 subunit carries out DNA binding, cleavage, and rejoining, while the B2 subunit mediates ATPase activity.
Anti-bacterial agents that target the A subunit, such as quinolones, now face growing resistance among clinically important bacterial pathogens. Attempts to inhibit the B subunit of gyrase instead have not been entirely successful. Agents that inhibit catalysis of ATP hydrolysis by the B subunit (e.g., coumarins, such as novobiocin, and the cyclothialidines) were found to have low antimicrobial activities and unfavorable toxicity profiles (not related to the mechanism of action). U.S. Pat. Nos. 6,608,087 and 6,632,809, both of which are hereby incorporated by reference, describe other gyrase inhibitors. U.S. Pat. Nos. 5,140,034; 5,208,248 and 6,555,539, each of which is incorporated by reference in its entirety, disclose thiazolyl indazoles and their use as therapeutic agents, but these compounds are not known to be useful for inhibiting the B subunit of gyrase.
A need therefore exists for new anti-bacterial compounds, and particularly those that target the B subunit of bacterial DNA gyrase while overcoming the drawbacks of the existing inhibitors.